Does the patch below help?

From: Bartlomiej Zolnierkiewicz <redacted>
Subject: [PATCH] blk-mq: fix undefined behaviour in order_to_size()

When this_order variable in blk_mq_init_rq_map() becomes zero
the code incorrectly decrements the variable and passes the result
to order_to_size() helper causing undefined behaviour:

 UBSAN: Undefined behaviour in block/blk-mq.c:1459:27
 shift exponent 4294967295 is too large for 32-bit type 'unsigned int'
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0-rc6-00072-g33656a1 #22

Fix the code by checking this_order variable for not having the zero
value first.

Reported-by: Meelis Roos <redacted>
Fixes: 320ae51feed5 ("blk-mq: new multi-queue block IO queueing mechanism")
Signed-off-by: Bartlomiej Zolnierkiewicz <redacted>

It fixes the warning independently of the pata driver - ata_piix 
pata_via pata_serverworks pata_macio 3ware were fixed too.

-- 
Meelis Roos (mroos@linux.ee)